2. (a) Krypton (noble gas) and Rubidium (Group I metal)Kr has a simple molecular structure and Rb has a giant metallic structure. Larger amount of energy is needed to overcome the stronger electrostatic attraction between Rb+ and its mobile electrons than the weaker van der Waals' forces between Kr atoms . Hence, boiling point of Rb is higher than that of Kr.

b) AlF3 and PF3 AlF3 has a giant ionic structure and PF3 has a simple molecular/ covalent structure. Larger amount of energy is needed to overcome the stronger electrostatic attraction between Al3+ and F( ions in AlF3 than the weaker intermolecular forces (or van der Waals' forces/ permanent dipole –permanent dipole attraction) between PF3 molecules. Hence, melting point of AlF3 is higher than that of PF3.

c) Diamond and siliconBoth diamond and silicon have giant molecular/ covalent structure. Since C is a smaller atom than Si, the C─C bond length is shorter than that of Si─Si bond, giving rise to stronger C─C covalent bond (bond energy of C─C bond is 350 kJ mol-1 versus Si─Si bond 222 kJ mol-1). Larger amount of energy is needed to overcome the stronger C─C bond than the weaker Si─Si bond. Hence, melting point of diamond is higher than that of silicon. 3. AlCl3 tends to dimerises to form Al2Cl6. At higher temperatures this Al2Cl6 dimer dissociates into trigonal planar AlCl3. [pic]

4.Simple covalent/molecular structure. Strong covalent bond between Se and O atoms and weak intermolecular forces between selenium dioxide molecules. udents to its (1) relatively low melting point and (2) Non-conductor of electricity due to absence of charged carriers.]

5.ACJC Prelim 01/2/2(a)Briefly explain the following observations.

AlF3 conducts electricity when molten but AlCl3 does not. AlF3 is essentially ionic, made up of oppositely charged Al3+ and F( ions. In the molten state, these charged ions are mobile and free to move about to carry charge and conduct electricity.

AlCl3, on the other hand, is essentially covalent. This is due to the polarisation of the large electron cloud of Cl( by the small and highly charged Al3+. In the molten state, AlCl3 exists as discrete molecules and there is an absence of charged particles in any state to conduct electricity.

6. IBoron trifluoride and not methane, will react with trimethylamine to form a 1:1 complex. The N atom on (CH3)3N has a lone pair for donation whilst the B atom on BF3 has an empty orbital to accept this pair of electrons to form a dative...

...Chapter 6 - Answer Key to Section Review 1-3
Section Review 1
1. What is the main distinction between ionic and covalent bonding?
Answer (A): Ionic bonding involves the electrical attraction between large numbers of anions and cations. Covalent bonding involves the sharing of electron pairs between two atoms.
Translation:
-Ionic bonding happens between a metal and a non-metal (east coast and west coast)
-One atom completely donates its valence electrons to another atom
-Metals become CATIONS (positive charge/oxidation state); Non-metals become ANIONS (negative charge/oxidation state)
Example: Na + Cl → Na+Cl- or Mg + O → Mg2+O2-
-In covalent bonding one atom completely shares its valence electrons with another atom (west coast and west coast)
Example: H2O, CO2
2. How is electronegativity used in determining the ionic or covalent character of the bonding between two elements?
A: A large difference in electronegativity between two atoms in a bond will result in ionic bonding. A small difference in electronegativity between two atoms will result in covalent bonding.
Translation: Electronegativity difference between 0-0.3 = Non-polar covalent bond
Electronegativity difference between 0.3-1.7 = Polar covalent bond
Electronegativity difference greater than 1.7 = Ionic bond
3. What type of...

...Intermolecular Bonding Essay
Write an essay on intermolecular bonding. Explain how each type of bond arises
and the evidence for the existence of each. Comment on their strengths in
relation to the types of atoms involved; the covalent bond and relative to each
other. Use the concepts of different types and strengths of intermolecular bonds
to explain the following:
There exists four types of intermolecular bonding, they include ionic, covalent,
Van der waals and hydrogen bonding. In order to describe the existence of such
bonding you must also understand the concepts of polarity, polar and non-polar,
and electronegativity.
Ionic bonds are created by the complete transfer of electrons from one atom to
another. In this process of electron transfer, each atom becomes a ion that is
isoelectronic with the nearest noble gas., the substance is held together by
electrostatic forces between the ions. The tendency for these ions to be formed
by elements is corespondent to the octet rule, when atoms react,, they tend to
do so in such a way that they attain an outer shell containing eight electrons.
The factors that effect the formation of ions are ionization energy, electron
affinity, lattice energy.
Figure 1
The transfer of electrons involved in the formation of (a) sodium chloride and
(b) calcium fluoride. Each atom forms an ion with an outer shell containing
eight electrons.
For many elements, compounds...

...molecules, when properly oriented, will attract each other as a result of this. Stronger than van der Waal's forces.
Hydrogen bonding -- When hydrogen is bonded to nitrogen, oxygen or fluorine, a very strong dipole is formed, making the hydrogen very strongly positive. This hydrogen is then attracted to the lone pairs on other similar molecules (nitrogen, oxygen and fluorine all have lone pairs) forming a hydrogen bond, which is stronger than van der Waal's or dipole-dipole, but weaker than covalent bonding.
The effect of hydrogen bonding on intermolecular forces can be demonstrated very well by studying the boiling points of the group 6 hydrides
b.p. comparison of main group hydrides
Order of priority
Hydrogen bonding strongest
Dipole -dipole interactions
Van der Waals forces
Hydrogen bonds result from hydrogen bonded as described above. This results in molecules with hydrogen bonding exhibiting stronger intermolecular forces, ie higher boiling/melting points etc. eg H2O has a higher bp then H2S due to hydrogen bonding, and so on down the strength list.
Water
Water has a very high melting and boline point due to extensive hydrogen bonding. Having two hydrogen it can form two H- bonds per molecule allowing a lattice diamond-like structure to be built up, as shown below in ice:
Ice structure showing the intermolecular hydrogen bonding...

...
7) Explain why the arrangement of electron pairs is tetrahedral in the the molecules above.
Each molecule has 4 atoms apart of the central atom.
8)H2S has two hydrogen atoms bonded to a sulfur atom. Why isn’t the molecule linear?
Since sulfur is the central atom and hydrogen’s valence electrons repels them away, it make a bent shape.
9) What is the arrangement of electron pairs in PBr3? Predict the molecular shape of a PBr3 molecule.
It is arranged tetrahedral because it has 3 atoms and a central atom.
10) Identify the the type of intermolecular bonding of a specific bond in H2O
London dispersion and hydrogen bonding.
11) Identify the the type of intermolecular bonding of a specific bond in BrCl
London dispersion
12) Identify the the type of intermolecular bonding of a specific bond in CH3OH
Hydrogen bonding, dipole dipole bonding, and London dispersion
13) A carbon monoxide molecule has a triple covalent bond because carbon and oxygen atoms have an unequal number of valence electrons
True/True
14) Xenon has a lower boiling point than neon because dispersion forces between xenon atoms are stronger than those between neon atoms.
False/True
15) The Nitrate ion has three resonance structures because the nitrate op has three single bonds.
True/False
...

...HYDROGEN BONDING:
Hydrogen bonding is a bonding type consisting of dipole and dispersion forces. A hydrogen bond is the attractive force between a hydrogen atom attached to a molecule and an atom of a different molecule.
According to the Pauling scale of electro-negativities of the elements, it can be viewed that the three most electronegative elements in the periodical table are nitrogen, oxygen and fluorine. These are also called heteroatoms. The heteroatoms have a partial negative charge while hydrogen has a partial positive charge.
Hydrogen bonding is generally stronger than most bonds bar covalent bonds.
Water:
Bonding within water molecules occur between oxygen and hydrogen. These covalent bonds mean that the electrons are shared between the oxygen and hydrogen atoms to create a complete valence shell. However, electrons tend to spend more time around the oxygen atom due to its higher electro-negativity. This creates a partial positive charge around the hydrogen atoms, and a partial negative charge around the oxygen atom. When other water molecules are present, the negatively charged end of one molecule will be attracted to the positively charged end of the other molecule, as shown below:
Hydrogen bonding is not a type of intramolecular force. Eg. Ionic, metallic and covalent bonding, it is an intermolecular force. An intramolecular force is one that exists between...